Many windows are manufactured for high energy efficiency by utilizing dual glazing panels with an insulating air space therebetween. Typically, the interior glazing panel is removable. Such a design requires that the insulating air space be vented to the atmosphere to prevent excessive moisture build up which results in condensation on the glazing panels. Such ventilation is usually provided by drilling holes through the sash frame. An example of this is shown in U.S. Pat. No. 4,627,206. A pair of drilled interconnecting holes are illustrated in prior art FIG. 6.
A breather system is needed that involves a minimum number of manufacturing steps but is effective in venting the insulating air space.